Apparatus and method for detecting electromagnetic wave source, and method for analyzing the same

ABSTRACT

There are provided electromagnetic wave source detecting apparatus and method as well as electromagnetic wave source analyzing system and method which can detect and analyze a source of (electromagnetic disturbing wave) representing a main factor in generating an electromagnetic field remotely of the apparatus in order to suppress the electromagnetic field intensity at the remote distance from the apparatus to below a regulated value. In the present invention, a magnetic field near an object  110  to be measured is measured by a set of at least two or more probes  101  and  102 , a position of an electromagnetic wave source is detected through simplified calculation of one function using a phase difference between the two probes, a current distribution on the measured object is determined by solving simultaneous equations containing the position information and magnitudes of measured magnetic fields and an electromagnetic field at a remote distance from the apparatus is determined from the current distribution, thereby identifying the source representing the main factor in generating the electromagnetic field remotely of the apparatus.

BACKGROUND OF THE INVENTION

The present invention relates to apparatus and method for detecting anelectromagnetic wave source which can detect and identify the positionof the source of an unwanted electromagnetic wave (electromagneticdisturbing wave) in an electronic apparatus such as a product mountingvarious kinds of electronic parts on a printed board, as well as systemand method for analyzing an electromagnetic wave source which cananalyze whether the standards of VCCI (Voluntary Control Council forInterference by Information Technology Equipment) are satisfied.

Electromagnetic interference due to an unwanted electromagnetic waveoccurs frequently concomitantly with the recent widespread use ofinformation communication apparatus and the like and therefore, inunwanted electromagnetic radiation suppressing technology, a techniquehas been required which can detect a source in order to suppress theunwanted electromagnetic wave (electromagnetic disturbing wave) which isthe cause of the electromagnetic interference.

Exemplified as conventional techniques concerning the method fordetection of an electromagnetic wave source are “A Proposal forSearching for Electromagnetic Wave Sources by Using a Synthetic ApertureTechnique” by Junichi Kikuchi et al, Transactions of the Institute ofElectronic Information and Communication Engineers of Japan, B-II,October 1985 (prior art 1), “Search for Electromagnetic Wave Sources byUsing Maximum Entropy Method” by Junichi Kikuchi et al, Transactions ofthe Institute of Electronic Information and Communication Engineers ofJapan, B-II, September 1986 (prior art 2), “Electromagnetic FieldMeasurement and Numerical Analysis for EMC Problems” by Sho-se Hayashi,NEC Techniques, September 1993 (prior art 3) and JP-A-4-329376 (priorart 4).

In the prior art 1, minute mono-pole antennas serving as electric fieldprobes are arrayed along a Cartesian coordinate system on a plane atintervals of about ¼ of the wavelength to obtain a result equivalent tothe measurement of an unwanted electromagnetic wave using anaperture-front antenna equal to the array area. A position on theaperture front where an electromagnetic wave source exist is identifiedfrom a phase shift of the measured value and the operation time can beshorter than that in other techniques and values of both the magnitudeand phase can be detected, but there arises a problem that theresolution is rough, amounting up to about ¼ of the wavelength.

In the prior art 2, the maximum entropy method is applied to time-seriesinformation of electromagnetic wave measured continuously for a constanttime to provide a power spectrum which in turn is made to correspond tothe position of an electromagnetic wave source in two-dimensional space.While the positional accuracy is high to advantage, there arise problemsthat measurement must continue for the constant time or more, phaseinformation of the source cannot be detected and a remote field cannotbe determined through calculation.

In the prior art 3, an electromagnetic wave source area is divided intominute gratings, simultaneous equations of current and magnetic fieldare set up by using the same number of measuring values as that ofgrating points and the equations are solved to identify theelectromagnetic wave source position. Given that the electromagneticwave source exists on the minute grating and the measuring value isstringently correct, the position can be obtained in the form of a pointand true values of the magnitude and phase can be obtained. But, if atleast one of the factors contains an error, then there will ariseproblems that the simultaneous equations do not converge and anysolution cannot be obtained or quite an erroneous solution iscalculated.

In the prior art 4, an electromagnetic field radiated from anelectromagnetic radiation source is measured by a stationary referenceantenna and a movable measuring antenna, the amplitude of anelectromagnetic field received by the measuring antenna and the phasedifference between electromagnetic fields measured by the referenceantenna and measuring antenna are used to provide a presumptiveexpression concerning distribution of electromagnetic disturbing sourcesand the position of an electromagnetic disturbing source is presumed bya spatial differential value of the presumptive expression. Accordingly,there arises a problem that unless the number of measuring pointsmeasured by the measuring antenna is considerably large, a point wherethe spatial differential value becomes large cannot be found and theaccuracy of presumption is degraded.

The present invention contemplates solving the above problems and anobject of the present invention is to provide electromagnetic wavesources detecting apparatus and method which can detect and identify asource of unwanted electromagnetic wave (electromagnetic disturbingwave) existing at an arbitrary position on an object to be measured withhigh accuracy and at a high rate by using a relatively small number ofmeasuring points for the purpose of suppressing the electromagneticfield at a remote location from the apparatus.

Another object of the invention is to provide electromagnetic wavesource analyzing system and method which can analyze and decide whetherthe measured object satisfies the VCCI standards.

Still another object of the invention is to provide electromagnetic wavesource analyzing system and method which can survey factors of a sourceof unwanted electromagnetic wave (electromagnetic disturbing wave)detected on the measured object.

SUMMARY OF THE INVENTION

To accomplish the above objects, an electromagnetic wave sourcedetecting apparatus according to the invention comprises a plurality ofprobes for measuring intensities Hm (inclusive of phase data) of anelectromagnetic field generated from an object to be measured of anelectronic apparatus at each measuring position (x_(m), y_(m)) whichchanges two-dimensionally along a measured object plane near themeasured object, and calculation means for calculating a phasedifference Δφ_(m)=(φ₂−φ₁)_(m) or time difference Δt_(m)=(t₂−t₁)_(m)between magnetic fields associated with the probes from theelectromagnetic field intensities Hm measured by the individual pluralprobes at each measuring position (x_(m), y_(m)), calculating adifference d between distances from a presumptive electromagnetic wavesource on the basis of the phase difference or time differencecalculated at each measuring position, determining a locus of thepresumptive electromagnetic wave source on the measured object planefrom the distance difference d and geometrical relations (for example,z₁, z₂) of the plurality of probes to the measured object and detectingan intersection of loci of the presumptive electromagnetic wave sourcewhich are determined at a plurality of measuring positions to calculateand identify a position (x_(s), y_(s))_(n) of an electromagnetic wavesource existing in the measured object.

Further, an electromagnetic wave source detecting apparatus according tothe invention comprises a plurality of probes for measuring intensitiesHm (inclusive of phase data) of an electromagnetic field generated froman object to be measured of an electronic apparatus at each measuringposition (x_(m), y_(m)) which changes two-dimensionally along a measuredobject plane near the measured object, and calculation means forcalculating a phase difference Δφ_(m)=(φ₂−φ₁)_(m) or time differenceΔt_(m)=(t₂−t₁)_(m) between magnetic fields associated with the probesfrom the electromagnetic field intensities Hm measured by the individualplural probes at each measuring position (x_(m), y_(m)), calculating adifference d between distances from a presumptive electromagnetic wavesource on the basis of the phase difference or time differencecalculated at each measuring position, determining a locus of thepresumptive electromagnetic wave source on the measured object planefrom the distance difference d and geometric relations (for example, z₁,z₂) of the plurality of probes to the measured object, detecting anintersection (x_(s), y_(s))_(n) of loci of the presumptiveelectromagnetic wave source which are determined at a plurality ofmeasuring positions to calculate and identify a position of anelectromagnetic wave source existing inside the measured object, andfurther calculating magnitude In of current in the electromagnetic wavesource existing at the identified position on the basis of theelectromagnetic field intensities Hm measured by the probes at eachmeasuring position.

Further, an electromagnetic wave source detecting apparatus according tothe invention comprises a plurality of probes for measuring intensitiesHm of an electromagnetic field generated from an object to be measuredof an electronic apparatus at each measuring position (x_(m), y_(m))which changes two-dimensionally along a measured object plane near themeasured object, and calculation means for calculating a phasedifference Δφ_(m)=(φ₂−φ₁)_(m) or time difference Δt_(m)=(t₂−t₁)_(m)between magnetic fields associated with the probes from theelectromagnetic field intensities Hm measured by the individual pluralprobes at each measuring position, calculating a difference d betweendistances from a presumptive electromagnetic wave source on the basis ofthe phase difference or time difference calculated at each measuringposition, determining a locus of the presumptive electromagnetic wavesource on the measured object plane from the distance difference d andgeometrical relations (for example, z₁, z₂) of the plurality of probesto the measured object, detecting an intersection (x_(s), y_(s))_(n) ofloci of the presumptive electromagnetic wave source which are determinedat a plurality of measuring positions to calculate and identify aposition of an electromagnetic wave source existing inside the measuredobject, and further calculating magnitudes In of current distributionsin a plurality of electromagnetic wave sources existing at individualplural positions identified similarly on the basis of theelectromagnetic field intensities Hm measured by the probes at eachmeasuring position.

Further, in the present invention, the plurality of probes in theelectromagnetic wave source detecting apparatus are arranged on the sameprobe axis at the individual measuring positions.

Further, in the present invention, the plurality of probes in theelectromagnetic wave source detecting apparatus are arranged on the sameprobe axis vertical to the measured object plane at the individualmeasuring positions (x_(m), y_(m)). In this case, the locus of thepresumptive electromagnetic wave source on the measured object plane isindicated by a radius a_(m).

Further, in the present invention, the calculation means of theelectromagnetic wave source detecting apparatus further calculatesinversely an electromagnetic field intensity En at a desired remotedistance on the basis of the calculated magnitude of a currentdistribution in the electromagnetic wave source existing at theidentified position on the measured object.

Further, in the present invention, the calculation means of theelectromagnetic wave source detecting apparats inversely calculates anelectromagnetic field intensity En at a desired remote distance on thebasis of the calculated magnitude of a current distribution in each ofthe plurality of electromagnetic wave sources existing at each of theidentified plural positions on the measured object.

Further, an electromagnetic wave source analyzing method according tothe invention collates a position of an electromagnetic wave sourceexisting on a measured object identified by using the aforementionedelectromagnetic wave source detecting apparatus with mountinginformation (for example, circuit diagrams or mounting diagrams) of themeasured object through, for example, display on a display unit. Thispermits electronic parts generating an unwanted electromagnetic wave(electromagnetic disturbing wave) to be ascertained.

Further, an electromagnetic wave source analyzing method according tothe invention analyzes whether an electromagnetic field intensity at adesired remote distance calculated by using the electromagnetic wavesource detecting apparatus satisfies the VCCI standards.

Further, an electromagnetic wave source detecting method according tothe invention comprises measuring intensities Hm of an electromagneticfield generated from an object to be measured of an electronic apparatusat each measuring position (x_(m), y_(m)) which changestwo-dimensionally along a measured object plane near the measured objectby using a plurality of probes, calculating a phase differenceΔφ_(m)=(φ₂−φ₁)_(m) or time difference Δt_(m)=(t₂−t₁)_(m) betweenmagnetic fields associated with the probes from the magnetic fieldintensities Hm measured at each measuring position (x_(m), y_(m)),calculating a difference d between distances from a presumptiveelectromagnetic wave-source on the basis of the phase difference or timedifference calculated at each measuring position, determining a locus ofthe presumptive electromagnetic wave source on the measured object planefrom the distance difference d and geometrical relations (for example,z₁, z₂) of the plurality of probes to the measured object, and detectingan intersection (x_(s), y_(s))_(n) of loci of the presumptiveelectromagnetic wave source which are determined at a plurality ofmeasuring positions to calculate and identify a position of anelectromagnetic wave source existing inside the measured object.

Further, an electromagnetic wave source detecting method according tothe invention comprises measuring intensities Hm of an electromagneticfield generated from an object to be measured of an electronic apparatusat each measuring position (x_(m), y_(m)) which changestwo-dimensionally along a measured object plane near the measured objectby using a plurality of probes, calculating a phase differenceΔφ_(m)=(φ₂−φ₁)_(m) or time difference Δt_(m)=(t₂−t₁)_(m) betweenmagnetic fields associated with the probes from the electromagneticfield intensities Hm measured at each measuring position, calculating adifference d between distances from a presumptive electromagnetic wavesource on the basis of the phase difference or time differencecalculated at each measuring position, determining a locus of thepresumptive electromagnetic wave source on the measured object planefrom the distance difference d and geometrical relations (for example,z₁, z₂) of the plurality of probes to the measured object, detecting anintersection (x_(s), y_(s))_(n) of loci of the presumptiveelectromagnetic wave source which are determined at a plurality ofmeasuring positions to calculate and identify an electromagnetic wavesource existing inside the measured object, and further calculatingmagnitude In of current in the electromagnetic wave source existing atthe identified position on the basis of the electromagnetic fieldintensities measured by the probes at each measuring position.

As described above, with the construction as above, by approaching onlymagnetic field probes small enough not to disturb magnetic fields fromthe main body of the measuring apparatus to the measured object, thepositions of electromagnetic wave sources existing at arbitrarypositions on the measured object can be presumed from the phaseinformation by reducing the number M of measuring points of magneticfield distribution without being affected by the influence of reflectionto obtain the number N (=M) of the sources, thereby ensuring that thepositions of the electromagnetic wave sources existing at the arbitrarypositions can be presumed with high accuracy and at a high rate.

Further, with the above construction, it can be analyzed and decidedwhether the measured object satisfies the VCCI standards.

Further, with the above construction, factors (kinds of electronicparts) of the source of unwanted electromagnetic wave (electromagneticdisturbing wave) detected on the measured object can be surveyed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an embodiment of an electromagneticwave source detecting apparatus according to the invention.

FIG. 2 is a schematic construction diagram showing an embodiment ofelectromagnetic wave source detecting apparatus and electromagnetic wavesource analyzing system according to the invention.

FIG. 3 is a diagram for explaining the outline of electromagnetic wavesource detecting algorithm according to the invention.

FIG. 4 is a partial explanatory diagram of the electromagnetic wavesource detecting algorithm.

FIG. 5 is a diagram showing the concept of space for currentdistribution calculation according to the invention.

FIG. 6 is an explanatory diagram of calculation of remoteelectromagnetic-field intensity according to the invention.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of electromagnetic wave source detecting apparatus andmethod as well as electro-magnetic wave source analyzing system andmethod according to the present invention will be described withreference to FIGS. 1 to 6.

The electromagnetic wave source detecting apparatus and electromagneticwave source analyzing system according to the invention are constructedas shown in FIGS. 1 and 2. FIG. 3 shows a conceptual diagram ofelectromagnetic wave source detecting algorithm according to theinvention. FIG. 4 shows an explanatory diagram of details of theelectromagnetic wave source detecting algorithm according to theinvention.

As shown in FIG. 1, the electromagnetic wave source detecting apparatus100 according to the invention has a probe 1 (101) and a phase referenceprobe 106 near a device to be measured (constructed by, for example,mounting various kinds of electronic parts on a printed board.) 110.Here, a phase φ1 of a magnetic field measured at a measuring position 1(107) of coordinates (x₁, y₁) determined by projecting the probe 1 (101)on the measured device 110 can be obtained as a phase differencerelative to a magnetic field detected by the phase reference probe 106provided at an arbitrary position.

From the phase φ1 of the magnetic field, a phase φ2 of the magneticfield at a measuring position 2 (108) of similarly determinedcoordinates (x₂, y₂) and a phase φ3 of the magnetic field at a measuringposition 3 (109) of similarly determined coordinates (x₃, y₃), distancesequal to the individual phase differences can be obtained and a solepoint with respect of which the phase differences are generated can beobtained as a position of an electromagnetic wave source 105.

The above technique is more generalized to lead to an electromagneticwave source detecting method based on phase detection which will bedescribed with reference to FIG. 2.

As shown in FIG. 2, in the electromagnetic wave source detectingapparatus 100 according to the invention, a main body of measuringapparatus constructed of the probes 1 (101) and 2 (102) is spaced apartfrom the measured device (constructed by, for example, mounting variouselectronic parts on a printed board.) 110 in order to decrease theinfluence of reflection and only magnetic field probes extending fromthe main body of measuring apparatus and being small enough not todisturb the magnetic field are positioned in close to the measureddevice 110. Namely, as shown in FIG. 4, in the electromagnetic wavesource detecting apparatus 100, the probe 1 (101) and probe 2 (102) aredisposed at distances 301 and 302 which are electromagnetically close tothe measured device 110 (defined by a current distribution identifyingplane 403 in FIG. 5.) at a point (defined for, for example, the probe 1as a magnetic field distribution measuring point 402 (x_(m), y_(m)) on atwo-dimensional field distribution measuring plane 401 in FIG. 5.). Theelectromagnetic wave source detecting apparatus 100 further comprises amoving mechanism 120 for moving these probe 1 (101) and probe 2 (102) tothe magnetic field distribution measuring point 402 (x_(m), y_(m)) andpositioning them there, a controller 121 for controlling an actuator inthe moving mechanism 120, a CPU 122 for identifying a position (currentdistribution identifying point 404) of the electromagnetic wave source105 existing inside the measured object (measured device) 110 andcalculating an electromagnetic field intensity at an arbitrary distancefrom the measured device, a display unit 124 for displaying the data asan output, input means 125 constructed of, for example, a recordingmedium, network or keyboard for inputting known data and informationabout mounting electronic parts in the measured device 110, and a memoryunit 123 for storing various kinds of data and information. Thecontroller 121 is so constructed as to deliver the position coordinates(x_(m), y_(m)) of the magnetic field distribution measuring point 402for the probe 1 (101) and probe 2 (102) to the CPU 122.

Incidentally, the probes 1 (101) and 2 (102) are for measurement ofmagnetic field and they can turn in individual x, y and z directions.They can otherwise be formed integrally. Namely, since magnetic fieldsH₁ and H₂ have each vector components, the probe 1 (101) is soconstructed as to be able to detect x direction component H_(1x), ydirection component H_(1y) and z direction component H_(1z) and theprobe 2 (102) is so constructed as to be able to detect x directioncomponent H_(2x), y direction component H_(2y) and z direction componentH_(2z). Accordingly, by using these probes 1 (101) and 2 (102), phasedifference measurement 201 as shown in FIG. 3 can be carried out nearthe measured device 110. Namely, with the respective probes 1 (101) and2 (102), the magnetic field H1 (having a phase of φ₁) and magnetic fieldH₂ (having a phase φ₂) from the measured object 110 which are expressedby the following equations (2) and (3) can be detected. Then, a phasedifference Δφ_(m)=(φ₂−φ₁)_(m) can be calculated and measured by means ofthe CPU 122 and the like connected with the probes 1 (101) and 2 (102).Here, the magnetic fields existing in the space confining the individualprobes can be expressed by the following equations (1) and (2).

H ₁ =f(I ₁ , r ₁)=|f(I ₁ , r ₁)|e ^(−jkr)1=|H ₁ |e ^(jφ)1  (1)

 H ₂ =f(I ₂ , r ₂)=|f(I ₂ , r ₂)|e ^(−jkr)2=|H ₂ |e ^(jφ)2  (2)

The phase difference Δφ_(m)=(φ₂−φ₁)_(m) can be determined by a wavenumber k=2π/λ=2πf/c determined by a frequency f to be measured(especially, electromagnetic field intensity EdBμV generated at afrequency of 100 MHz to 1 GHz or more matters.) and distances r₁ and r₂between the electromagnetic wave source 105 and the individual probesand can be expressed by the following equation (3), where c representsvelocity of light (velocity of electromagnetic wave).

Δφ_(m)=(φ₂−φ₁)_(m) =k(r ₁ −r ₂)  (3)

Given that the difference between the distance r₁ from theelectromagnetic wave source 105 to the probe 1 (101) and the distance r₂from the electromagnetic wave source 105 to the probe 2 (102) is d_(m)(303), the relation indicated by the following equation (4) stands.

(r1−r2)=(φ₂−φ₁)_(m) /k=Δφ_(m) /k=d _(m)  (4)

Consequently, as shown in FIG. 4, a calculated radius a (104) from thepoint determined by projecting a probe axis 202 on the measured object110 can be determined from a distance difference d which is calculatedfrom the phase difference Δφ_(m)=(φ₂−φ₁)_(m) between the measuredmagnetic fields on the basis of the aforementioned equation (4) and canbe expressed by a simple function as indicated by the following equation(5), where z₁ and z₂ represent heights of the probes 1 (101) and 2 (102)from the measured device 110, respectively, and can be acquired via thecontroller 121 from the mechanism 120 for positioning the probes 1 (101)and 2 (102) in the height direction. Accordingly, the CPU 122 calculatesthe radius a (104) from the point determined by projecting the probeaxis 202 on the measured object 110 and stores it, along with coordinateinformation (x_(m), y_(m)) of the probe axis 202, in the memory unit123. The coordinate information (x_(m), y_(m)) of the probe axis 202 canof course be acquired, through the controller 121, from the mechanism120 for two-dimensionally moving the probes 1 (101) and 2 (102) andpositioning them. $\begin{matrix}{a = {\sqrt{\left( \frac{z_{1}^{2} - z_{2}^{2} - d^{2}}{2d} \right)^{2}} - z_{2}^{2}}} & (5)\end{matrix}$

Instead of calculating and measuring the phase differenceΔφ_(m)=(φ₂−φ₁)_(m) on the basis of the magnetic fields H₁ and H₂ of themeasured object detected by the respective probes 1 (101) and 2 (102) atthe measuring position (x_(m), y_(m)), the CPU 122 may calculate andmeasure a time difference Δt_(m)=(t₂−t₁)_(m) (time differencemeasurement 219) as shown in FIG. 3. More particularly, on the basis ofthe time difference Δt_(m)=(t₂−t₁)_(m) between rise timings of timewaveforms, fall timings of time waveforms or timing for exceeding athreshold and timing for falling below the threshold, the distancedifference d (303) can be sought and determined from the relationindicated by the following equation (6). In the CPU 122, this issubstituted to the equation (5) to seek and determine the distancedifference d (104) between the position of the electromagnetic wavesource 105 and the point determined by projecting the probe axis 202 onthe measured object 110.

d _(m) =Δt _(m) xc  (6)

where c represents the velocity of light (velocity of electromagneticwave) which is a known value.

Gathering from the above results, the CPU 122 knows that theelectromagnetic wave source 105 is on a circumferential locus(point-symmetrical to the probe axis 202) 103 having a radius a₁ (104)centered on the point (x₁, y₁) determined by projecting the probe axis202 on the measured object 110. The CPU 122 stores, as a detectionresult 1 (103), the circumferential locus 103 on which theelectromagnetic wave source 105 is presumed to exist in the memory unit123. Further, similar measurement is carried out by changing theposition of the probe axis 202 to (x₂, y₂) and (x₃, y₃) and the results(circumferential locus 103 b of radius a₂ and circumferential locus 103c of radius a₃) are stored as detection results 2 (103 b) and 3 (103 c),respectively, in the memory unit 123. Then, the CPU 122 can determineand identify a position where the electromagnetic wave source 105 existsat a sole intersection of these circumferential loci 103, 103 b and 103c. Given that the position of the probe axis 202 changes to coordinates(x₂, y₂) and coordinates (x₃, y₃) and radii are a₂ and a₃, the CPU 122can calculate the intersection in terms of coordinates (x_(s), y_(s)) ofthe electromagnetic wave source 105 by solving the following equation(7).

(x _(s) −x ₁)²+(y _(s) −y ₁)² =a ₁ ²

(x _(s) −x ₂)²+(y _(s) −y ₂)² =a ₂ ²

(x _(s) −x ₃)²+(y _(s) −y ₃)² =a ₃ ²  (7)

As described above, the CPU 122 can calculate and identify the positioncoordinates (x_(s), y_(s))_(n) of the electromagnetic wave source 105(current distribution identifying point 404) existing at an arbitraryposition #N on the measured object 110 (current distribution identifyingplane 403) and can store it in, for example, the memory unit 123.

The above measurement is effected near the measured object 110 on thebasis of a command from the CPU 122 by changing the probe axis 202 to aplurality of locations (indicated by #1 to #M in FIG. 5.), so thatconditions of distribution of electromagnetic wave sources 105 (currentdistribution identifying points 404) existing at arbitrary positions onthe measures object 110 (current distribution identifying plane 403) asshown in FIG. 5 can be known. The number N is made to be equal to thenumber M of these points.

Here, by holding intensity information Hm(M)=[Hmx(M), Hmy(M), Hmz(M)],along with phase information φm(M), in the memory unit 123 and bycausing the CPU 122 to substitute magnetic field distribution measuringvalues Hm(M)=[Hmx(M), Hmy(M), Hmz(M)] of the same number as the number Nof the current distribution identifying points 404 to the followingequation (8), magnitude I=[Ix(N), Iy(N), Iz(N)] of a currentdistribution in the electromagnetic wave source 105 (currentdistribution identifying point 404) existing at an arbitrary position #Nand phase φ(N) of the current can be calculated and stored in the memoryunit 123. The current I(N) is related to the phase φ(N) by equation (9)as below. $\begin{matrix}{\begin{pmatrix}{{Hm}_{x}(M)} \\{{Hm}_{y}(M)} \\{{Hm}_{z}(M)}\end{pmatrix} = {\begin{pmatrix}{{Hx}_{x}\left( {M,N} \right)} & {{Hx}_{y}\left( {M,N} \right)} & {{Hx}_{z}\left( {M,N} \right)} \\{{Hy}_{x}\left( {M,N} \right)} & {{Hy}_{y}\left( {M,N} \right)} & {{Hy}_{z}\left( {M,N} \right)} \\{{Hz}_{x}\left( {M,N} \right)} & {{Hz}_{y}\left( {M,N} \right)} & {{Hz}_{z}\left( {M,N} \right)}\end{pmatrix} \cdot \begin{pmatrix}{I_{x}(N)} \\{I_{y}(N)} \\{I_{z}(N)}\end{pmatrix}}} & (8)\end{matrix}$

Since the coordinates (x_(m), y_(m)) of #M at which the probe axis 202is positioned, the height data of, for example, the probe 1 (101)(magnetic field distribution measuring plane 401) caused to approach themeasured device 110 (current distribution identifying plane 403) and theposition coordinates (x_(sn), y_(sn)) of the electromagnetic wave source105 (current distribution) existing at the arbitrary position #Ncalculated and identified as above are known, the CPU 122 can determinecoefficients [Hx_(x)(M, N), Hx_(y)(M,N), Hx_(z)(M, N); Hy_(x)(M, N),Hy_(y)(M, N), Hy_(z)(M, N); Hz_(x)(M, N), Hz_(y)(M, N), Hz_(z)(M, N)].Accordingly, by solving the aforementioned equation (8) on the basis ofthe measured magnetic field distribution measuring values Hm(M)=[Hmx(M),Hmy(M), Hmz(M)], the CPU 122 can calculate magnitude I=[Ix(N), Iy(N),Iz(N)] of the current distribution in the electromagnetic wave source105 (current distribution identifying point 404) existing at thearbitrary position #N and phase φ(N) of the current.

I(N)=|I(N)|e ^(jφ(N))  (9)

Further, as shown in FIG. 6, by calculating electromagnetic fieldintensity E(n)=[Eφ, Eθ] at an arbitrary distance (regulateddistance)r_(n) (distance regulated by VCCI (Voluntary Control Councilfor Interference by Information Technology Equipment)) from the measuredobject 110 pursuant to the following equation (10) on the basis of thecurrent distribution [Ix(n), Iy(n), Iz(n)] calculated at the currentdistribution identifying point n, storing it in the memory unit 133 anddelivering the stored electromagnetic field intensity E(n)=[Eφ, Eθ] atthe regulated distance r_(n) so as to display it on, for example, thedisplay unit 124, the CPU 122 can compare the intensity with a regulatedvalue of the VCCI. The equation (10) as below indicates electromagneticfield intensities (Eφ, Eθ) in φ direction and θ direction generated atthe distance r_(n) by the current (Ix(n), Iz(n)) flowing through minutelengths (dI_(xn), dI_(zn)). Obviously, the CPU 122 may decide whetherthe electromagnetic field intensity E(n)=[Eφ, Eθ] at the calculatedregulated distance r_(n) meets the VCCI standards and deliver the resultby using output means such as the display unit 124. $\begin{matrix}\begin{matrix}{E_{\varphi} = \quad {\sum\limits_{n = 1}^{N}{\frac{\eta}{2\quad \lambda \quad r_{n}}\left( {{{{- {{Ix}(n)}} \cdot {dl}_{xn}}\sin \quad \varphi} + {{{{Iy}(n)} \cdot {dl}_{yn}}\cos \quad \varphi}} \right.}}} \\{\quad {{\left\lbrack {1 + \left( {\frac{1}{j\quad {kr}_{n}} - \frac{1}{k^{2}r_{n}^{2}}} \right)} \right\rbrack \cdot ^{{- j}\quad {kr}}}n}} \\{E_{\theta} = \quad {\sum\limits_{n = 1}^{N}{\frac{\eta}{2\quad \lambda \quad r_{n}}\left( {{{{Iz}(n)} \cdot {dl}_{zn}}\sin \quad {{\varphi \left\lbrack {1 + \left( {\frac{1}{j\quad {kr}_{n}} - \frac{1}{k^{2}r_{n}^{2}}} \right)} \right\rbrack} \cdot ^{{- j}\quad {kr}}}n} \right.}}}\end{matrix} & (10)\end{matrix}$

where η=120π, λ=c/f, k=π/λ, c: velocity of light.

In the above detecting method, a set of probes 1 (101) and 2 (102)arranged on the probe axis 202 is not always required to be arrangedvertically to the measured object 110 as shown in FIGS. 2 to 4 but theprobe axis 202 may be disposed obliquely to or laterally of the measureddevice (measured object) 110. In this case, in the calculation of theradius a (104) pursuant to the equation (5) and the calculation of theelectromagnetic wave source 105 pursuant to the equation (7), thecircular locus (point-symmetrical to the probe axis 202) of the radius awith respect to an axial direction vector (a vector oblique to orlateral of the measured object 110) of the probe set disposed on theprobe axis 202 may be generalized to an elliptical locus or an ovallocus obtained by projecting the circular locus on the plane of themeasured device 110, and an intersection of these loci corresponding tothe position at which the electromagnetic wave source 105 exists may becalculated.

Besides, when the probe 2 (102) is fixed at one point to serve as thephase reference probe as shown in FIG. 1, the position detecting methodcoincides with the method for detecting the position of theelectromagnetic wave source based on the phase detection as explained inthe beginning. But in this case, the calculation process becomescomplicated and time-consuming and the accuracy is degraded.

Next, an embodiment will be described in which it is searched, on thebasis of distribution conditions of the electromagnetic wave sources 105(current distribution identifying points 404) identified on the measureddevice 110 (current distribution identifying plane 403) as describedpreviously, what electronic parts the source is constructed of. In casethe measured device 110 is constructed by, for example, mounting variouskinds of electronic parts on a printed board, such CAD mountinginformation is inputted from a CAD system in advance by means of inputmeans 125 constructed of a network or a recording medium and stored inthe memory unit 123. Besides, an image obtained by actuallyphotographing a product mounting various kinds of electronic parts onthe printed board is inputted by means of the input means 125constructed of a network or a recording medium and is stored in thememory unit 123. In this manner, mounting information (for example,circuit diagrams and mounting diagrams) of an electronic apparatusrepresenting the measured object 110 is stored, as a file or an image,in the memory unit 123.

Then, by collating the position information of the identifiedelectromagnetic wave source 105 (current distribution identifying point404) with the precedently inputted mounting information of electronicapparatus for the measured object 110 on, for example, the screen of thedisplay unit 124, the CPU 122 can search what factors (for example,kinds of electronic parts) the electromagnetic wave source isconstructed of and as a result, measures (for example, alteration ofdesign or exchange of parts) of, for example, weakening the generationof the electromagnetic wave can be applied.

Advantageously, according to the invention, an unwanted electromagneticwave source existing at an arbitrary position on the measured object ofelectronic apparatus can be detected with high accuracy and at a highrate so as to be presumed.

Besides, according to the invention, by holding absolute valueinformation during electromagnetic field measurement and substitutinginformation of magnetic field distribution corresponding in number tothe presumed electromagnetic wave sources to simultaneous equations, theposition of the electromagnetic wave source on the measured object,along with the magnitude and phase of current, can be determined withhigh accuracy and at a high rate to advantage.

Further, according to the invention, by calculating an electromagneticfield intensity at an arbitrary remote distance from the measured objectthrough the use of the position of the electromagnetic wave source onthe measured object and information about the magnitude of current, acomparative decision as to whether the VCCI standards are satisfied canalso be made.

Further, according to the invention, by permitting calculation of remoteelectromagnetic field intensity, an unwanted electromagnetic wave sourcecan be detected within a short period and with high accuracy and as aresult, measures against unwanted electromagnetic wave are not appliedto a location where design quality does not matter and the efficiency ofdesign can greatly be promoted to advantage.

What is claimed is:
 1. An electromagnetic wave source detectingapparatus comprising: a plurality of probes for measuring intensities ofan electromagnetic field generated from an object to be measured of anelectronic apparatus at each measuring position; and calculation meansfor calculating a phase difference or time difference between magneticfields associated with said probes from the electromagnetic fieldintensities measured by the individual plural probes at each measuringposition, determining a locus of a presumptive electromagnetic wavesource on the measured object plane on the basis of the phase differenceor time difference calculated at each measuring position, and detectingan intersection of loci of the presumptive electromagnetic wave sourcewhich are determined at a plurality of measuring positions to calculateand identify a position of an electromagnetic wave source existing insaid measured object.
 2. An electromagnetic wave source detectingapparatus according to claim 1, wherein said plurality of probes arearranged on the same probe axis at the individual measuring positions.3. An electromagnetic wave source detecting apparatus according to claim1, wherein said plurality of probes are arranged on the same probe axisvertical to said measured object plane at the individual measuringpositions.
 4. An electromagnetic wave source analyzing method comprisingcollating a position of an electromagnetic wave source existing on ameasured object identified by using the electromagnetic wave sourcedetecting apparatus as recited in claim 1 with information as to amounting state of said measured object.
 5. An electromagnetic wavesource detecting apparatus comprising: a plurality of probes formeasuring intensities of an electromagnetic field generated from anobject to be measured of an electronic apparatus at each position; andcalculation means for calculating a phase difference or time differencebetween magnetic fields associated with said probes from theelectromagnetic field intensities measured by the individual pluralprobes at each measuring position, determining a locus of a presumptiveelectromagnetic wave source on the measured object plane on the basis ofthe phase difference or time difference calculated at each measuringposition, detecting an intersection of loci of the presumptiveelectromagnetic wave source which are determined at a plurality ofmeasuring positions to calculate and identify a position of anelectromagnetic wave source existing inside said measured object andfurther calculating magnitude of a current in the electromagnetic wavesource existing at the identified position on the basis of theelectromagnetic field intensities measured by said probes at eachmeasuring position.
 6. An electromagnetic wave source detectingapparatus according to claim 5, wherein said plurality of probes arearranged on the same probe axis at the individual measuring positions.7. An electromagnetic wave source detecting apparatus according to claim5, wherein said plurality of probes are arranged on the same probe axisvertical to said measured object plane at the individual measuringpositions.
 8. An electromagnetic wave source detecting apparatusaccording to claim 5, wherein said calculation means further calculatesinversely an electromagnetic field intensity at a desired remotedistance on the basis of the calculated magnitude of a current in theelectromagnetic wave source existing at the identified position on saidmeasured object.
 9. An electromagnetic wave source analyzing methodcomprising analyzing whether an electromagnetic field intensity at adesired remote distance calculated by using the electromagnetic wavesource detecting apparatus as recited in claim 8 satisfies the VCCIstandards.
 10. An electromagnetic wave source detecting apparatuscomprising: a plurality of probes for measuring intensities of anelectromagnetic field generated from an object to be measured of anelectronic apparatus at each measuring position; and calculation meansfor calculating a phase difference or time difference between magneticfields associated with said probes from the electromagnetic fieldintensities measured by the individual plural probes at each measuringposition, determining a locus of a presumptive electromagnetic wavesource on the measured object plane on the basis of the phase differenceor time difference calculated at each measuring position, detecting anintersection of loci of the presumptive electromagnetic wave sourcewhich are determined at a plurality of measuring positions to calculateand identify a position of an electromagnetic wave source existinginside said measured object, and further calculating magnitudes ofcurrent distribution in a plurality of electromagnetic wave sourcesexisting at individual plural positions identified similarly on thebasis of the electromagnetic field intensities measured by said probesat each measuring position.
 11. An electromagnetic wave source detectingapparatus according to claim 10, wherein said plurality of probes arearranged on the same probe axis at the individual measuring positions.12. An electromagnetic wave source detecting apparatus according toclaim 10, wherein said plurality of probes are arranged on the sameprobe axis vertical to said measured object plane at the individualmeasuring positions.
 13. An electromagnetic wave source detectingapparatus according to claim 10, wherein said calculation means furthercalculates inversely an electromagnetic field intensity at a desiredremote distance on the basis of the calculated magnitude of a currentdistribution in each of the plurality of electromagnetic wave sourcesexisting at each of the identified plural positions on said measuredobject.
 14. An electromagnetic wave source analyzing method comprisinganalyzing whether an electromagnetic field intensity at a desired remotedistance calculated by using the electromagnetic wave source detectingapparatus as recited in claim 13 satisfies the VCCI standards.
 15. Anelectromagnetic wave source detecting method comprising the steps ofmeasuring intensities of an electromagnetic field generated from anobject to be measured of an electronic apparatus at each measuringposition by using a plurality of probes, calculating a phase differenceor time difference between magnetic fields associated with said probesfrom the magnetic field intensities measured at each measuring position,determining a locus of a presumptive electromagnetic wave source on themeasured object plane on the basis of the phase difference or timedifference calculated at each measuring position, and detecting anintersection of loci of the presumptive electromagnetic wave sourcewhich are determined at a plurality of measuring positions to calculateand identify a position of an electromagnetic wave source existinginside said measured object.
 16. An electromagnetic wave sourcedetecting method comprising the steps of measuring intensities of anelectromagnetic field generated from an object to be measured of anelectronic apparatus at each measuring position by using a plurality ofprobes, calculating a phase difference or time difference betweenmagnetic fields associated with said probes from the electromagneticfield intensities measured at each measuring position, determining alocus of a presumptive electromagnetic wave source on said measuredobject plane on the basis of the phase difference or time differencecalculated at each measuring position, detecting an intersection of lociof the presumptive electromagnetic wave source which are determined at aplurality of measuring positions to calculate and identify anelectromagnetic wave source existing inside said measured object, andfurther calculating magnitude of a current in the electromagnetic wavesource existing at the identified position on the basis of theelectromagnetic field intensities measured by said probes at eachmeasuring position.
 17. An electromagnetic wave source detectingapparatus comprising: a plurality of probes for measuring intensities ofan electronic field or magnetic field generated from an object to bemeasured of an electronic apparatus at each measuring position; andcalculating means for calculating a phase difference or time differencebetween electric fields or magnetic fields associated with said probesfrom the intensities measured by the individual plural probes,calculating and identifying a position of an electromagnetic wave sourceexisting in said object to be measured by using the phase difference ortime difference thus calculated.